What Are PHAs in Cosmetics?
In dermo-cosmetics, the acronym PHA stands for Polyhydroxy Acids. This is a family of chemical exfoliants considered to be the third generation after AHAs (alpha-hydroxy acids) and BHAs (salicylic acid). Developed in the late 1990s, PHAs are known for their gentle exfoliating action, which is particularly well-tolerated by sensitive, thin, mature, couperose, or rosacea-prone skin.
This term has no connection to industrial “PHA” (polyhydroxyalkanoate), a biodegradable bioplastic used in packaging: these are two completely distinct families of molecules.
What are the main PHA acids used in cosmetics?
Three molecules make up the majority of the PHA active ingredients used in cosmetic formulas:
- Gluconolactone (the lactone form of gluconic acid): the most widely used PHA, which acts as an exfoliant, humectant, and antioxidant.
- Lactobionic acid: a moisturizing and antioxidant disaccharide, specifically formulated for sensitive skin and post-dermatological procedure care.
- Maltobionic acid: similar to lactobionic acid, valued for its effect on the elasticity and firmness of mature skin.
These three molecules share a common structural feature: the presence of multiple hydroxyl groups and a larger molecular weight than that of conventional AHAs (glycolic acid weighs approximately 76 g/mol, gluconolactone 178 g/mol, and lactobionic acid 358 g/mol). This larger size explains their slower penetration and excellent skin tolerance.
What is the difference between PHAs, AHAs, and BHAs?
The three families of chemical exfoliants have distinct modes of action:
- AHAs (glycolic, lactic, and mandelic acids): water-soluble, small molecular size, rapid and deep penetration into the stratum corneum. Powerful effect on skin radiance, but may cause photosensitivity and an increased risk of irritation.
- BHA (salicylic acid): Lipophilic, capable of penetrating the pore opening. The go-to choice for combination to oily skin prone to breakouts.
- PHAs (gluconolactone, lactobionic acid, maltobionic acid): large molecular size, more superficial penetration, and a more gradual exfoliating action. Better tolerated by the most sensitive skin types, they also combine moisturizing and antioxidant effects.
PHAs do not automatically replace AHAs or BHAs: they expand the range of options, particularly for skin types that cannot tolerate traditional exfoliants.
For which skin types are PHAs recommended?
PHAs are particularly well-suited for several skin types:
- Sensitive and reactive skin that does not tolerate AHAs or BHAs well.
- Skin affected by rosacea or couperose, as a complementary cosmetic treatment and following a dermatologist’s recommendation for active formulations.
- Delicate, dehydrated skin, or skin with a compromised skin barrier.
- Mature skin seeking a gentle, gradual smoothing effect.
- Skin that has recently undergone a dermatological procedure (chemical peel, laser treatment, microneedling): PHAs are often incorporated into recovery routines upon professional advice.
Those with eczema, psoriasis, or active dermatitis during a flare-up must consult a dermatologist before introducing any chemical exfoliant.
What benefits can you expect from PHAs?
PHAs combine several beneficial mechanisms of action into a single active ingredient:
- Gentle chemical exfoliation: gradual removal of cells at the end of their life cycle, without mechanical aggression.
- Moisturizing effect: hydroxyl groups attract and retain water in the stratum corneum, unlike AHAs, which can dry out the skin.
- Antioxidant action: gluconolactone and lactobionic acid chelate certain metal ions involved in oxidative stress.
- Support for the skin barrier: unlike aggressive exfoliation, PHAs preserve the integrity of the hydrolipidic film.
- Compatibility with other active ingredients: They can be combined with niacinamide,hyaluronic acid, or cosmetic retinol, often with less tightness than traditional AHAs.
How can you incorporate PHAs into your skincare routine?
Introducing PHAs follows the same principles as any chemical exfoliation:
- Perform a preliminarytolerance test on a small area (inner arm or behind the ear) for 2 to 3 days.
- Start by applying 2 to 3 times a week in the evening, then adjust based on your skin’s tolerance.
- Apply to clean, dry skin, avoiding the eye area and mucous membranes.
- Follow with a suitable moisturizer.
- In the morning, always apply sunscreen with SPF 30 to 50.
- Do not combine PHA with other chemical exfoliants on the same evening.
For skin that has never been exfoliated, a gentle PHA-based peel is often the most comfortable way to start.
PHAs and photosensitization: What are the risks?
Available studies suggest that PHAs cause less photosensitization than traditional AHAs. This is largely due to their larger molecular size, which limits penetration and the effect on the renewal of deeper skin layers. Some data even suggest that gluconolactone and lactobionic acid may offer partial protection against UV-induced free radicals.
However, as with any chemical exfoliant, daily sunscreen with an SPF of 30 to 50 remains essential: it is still the primary measure for preventing photoaging, regardless of the exfoliant chosen.
PHAs and Pregnancy: What Precautions Should You Be Aware Of?
Specific data on the use of PHAs during pregnancy and breastfeeding remain limited. Given their low skin penetration and excellent safety profile, they are generally considered to pose a lower risk than high-concentration AHAs or retinoids.
As a precaution, consult your pharmacist or doctor before any prolonged use during pregnancy or breastfeeding, especially for high concentrations (cosmetic peels). If in doubt, opt for skincare products specifically formulated to be “pregnancy-friendly.”
PHAs and Sensitive Skin: Why Are They Particularly Suitable?
Several clinical studies (Edison et al. 2008; Grimes et al. 2004) have documented that PHAs are better tolerated by patients with reactive, atopic, or rosacea-prone skin, or those who have recently undergone a dermatological procedure. The reasons identified are:
- Slower and more superficial penetration, which reduces the risk of stinging and redness.
- A compensatory moisturizing effect, which maintains skin comfort during exfoliation.
- Intrinsic antioxidant action that limits oxidative stress induced by exfoliation.
For extremely reactive skin, start with the lowest concentrations (≤ 5% gluconolactone) before considering more concentrated formulas.
How to Choose a PHA Skincare Product?
Several criteria guide the choice of a PHA-based exfoliating skincare product:
- Concentration: between 4% and 10% for regular at-home use.
- Formulation: serum, fluid, cream, mask, or lotion, depending on personal preference.
- Combination formulas: combinations of PHA + niacinamide, PHA + hyaluronic acid, and PHA + antioxidants (vitamin E, polyphenols) are very common.
- Denatured alcohol listed at the beginning of the INCI list: avoid if you have sensitive skin, even though sensitive skin is the natural target for PHAs.
- Consult a pharmacist or dermatologist if you have an associated skin condition (rosacea, eczema).
Start by using PHAs alone for the first few weeks, then gradually combine them with the other active ingredients in your skincare routine to assess individual tolerance.
